THE two parts of Ireland are responding in sharply different ways to the challenge of change as they await the arrival of President Clinton later this week.
In the heavily Roman Catholic Republic of Ireland the people voted last Friday by a wafer-thin majority to end a 58-year-old ban on divorce and remarriage.
In British-administered Northern Ireland, where Protestants dominate, the 15-month-old peace process appeared mired by mistrust between the two religious communities and misunderstandings between London and Dublin.
Opponents of divorce in the republic vowed Sunday to mount a legal challenge to the referendum's outcome.
Rory O'Hanlon, a leader of the No Divorce campaign, spoke of ''a grave offense against natural law'' and claimed that the winning margin of 9,124 votes out of 1.6 million cast was too narrow to justify such radical change.
Irish Prime Minister John Bruton expressed ''great relief'' at the outcome. Meanwhile, his officials were drafting fresh proposals aimed at breaking the Northern Ireland deadlock.
But when Dublin's new ideas reached London late Sunday, a spokesman for Prime Minister John Major said they ''contained nothing new.'' Messrs. Major and Bruton spoke to each other by telephone yesterday in a final bid to sort out their differences before Mr. Clinton's visit.
THE slender referendum victory (50.2 percent) disguised a large change in public sentiment.
In a 1986 referendum, 63 percent voted ''no'' to allowing divorce. This time, the increased support for change was most marked in cities. In Dublin, all 11 constituencies voted for divorce. In rural areas, the ''no'' vote prevailed.
Bruton and other political leaders pointed out during the campaign that Ireland, where four-fifths of the population are practicing Catholics, was alone in the 15-nation European Union in outlawing divorce. Michael Noonan, the minister in charge of the government campaign, said a decisive factor was age, with young voters opting for ''a break with the past.''
Under the new rules, separated couples who have lived apart for 4 out of the previous 5 years will be allowed to remarry. The Catholic Church's hierarchy opposed the change. Bishop Thomas Flynn, its spokesman, said Sunday after the result that Catholics whose marriages broke down ''must not be separated from the church.''
Mr. O'Hanlon and other ''no'' lobbyists said yesterday they would argue that the government had acted unconstitutionally by spending 500,000 Irish pounds ($750,000) to advertise the referendum. But government officials appeared confident that attempts to overturn the referendum verdict would fail.
During the campaign a Dublin court ruled that government-sponsored advertisements amounted to support for the ''yes'' vote. The ads were withdrawn.
The Irish government said Sunday that it would complain to the Vatican about comments made by Pope John Paul II just before the day of the vote. The pope urged a group of Irish Catholic pilgrims to ''reflect on the unbreakable bond of marriage.''
In recent years members of the clergy in Ireland have been involved in sexual scandals that may have undermined the Catholic Church's influence. Opinion is divided in Ireland over whether swings toward apparently more liberal attitudes on social issues will persuade Northern Ireland's Protestants to look more favorably on their neighbors across the border.
John Taylor, deputy leader of Northern Ireland's main Unionist party, said the result would ''not make me want to have closer links with the republic.''
''They have divorce in France, and I don't want any closer links with France,'' Mr. Taylor said.